Rhino 6 block edit dialogue box missing

Has the block edit option in R6 disappeared? None of the block edit commands are opening the edit dialogue box. (the box usually asks if you want to add, subtract or change base point.)

I’m trying to put a new base point on a block. It also means I can’t get out of block edit which is a topic that was resolved in V5.

I’m using dual monitors but even if I switch off my second monitor I can’t see the dialogue box anywhere.

I found the solution in the following thread.

Rhino 6 - Can't exit blocks